The invention relates to a brake signal conversion device which is used in combined operations involving railroad cars with different brake signal modes, in which the brake signals for one of the cars are converted to make them suitable for use by cars of a different brake signal mode on the same side, by converting the signals in a device in which, when a brake signal is output by one of the cars, it is converted and transmitted to the other car, and at the same time, has the ability to prevent the transmission of brake signals from the second car back to the first car.